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microscope set up is about
500—lOOOX
of the numerical aperture of the
objective to be used. Note that in photomicrography it is useless to
raise the magnification beyond the resolving power of the emulsion
(usually about
0.05mm).
However,
since the resolution of the emulsion
is
higher than that of the naked eye, photographs are usually taken at
a lower magnification and thereafter they are enlarged.
•
Real field of view (in mm) represents the extent of the object that comes
under observation. In higher magnification it becomes extremely
small.
Consequently, it is advisable to take aim at the object point to be exa-
mined
first under lower magnification and then revolve the nosepiece to
higher magnification.
•
When focus is on the center of the
field,
its circumference will usually be
blurred,
because a curvature of the image plane is unavoidable in the
microscope, except when using a plan type objectives. In order to get
sharp corner image, it is necessary to adjust the fine focusing knob and
switch the focus from the center onto the corners.
•
Depth of focus represents the thickness or height of the object in fi sharply
seen when observation is made through the microscope. In photomicrogra-
phy the depth of focus becomes smaller than the figure shown in the
previous table. Therefore, careful attention must be made in focusing
when
taking
microscope pictures.
By closing the condenser diaphragm, the depth of field can be made
greater than the value shown in the table.
4.
Condensers
Type
Numerical Aperture
Remarks
Abbe
1.30
Two lenses
For central illumination (without oblique illumination slider)
Abbe
1.30
Two lenses
For central and oblique illumination (with oblique
illumi-
nation
slider)
Aplanatic
1.40
Three
lenses
For high-class microscopy
Achromatic
1.25
Five
lenses
For high-class microscopy
Achromatic
(long focal-length type)
0.7
Four
lenses
Long focal-length type. Working distance 12mm. With
turret-mounted
annular diaphragms for phase-contrast and
phase-interference microscopy.
Universal Dark-Field
Condenser
1.20-1.40
for
dark-field
Supplied in centerable mount. With outer diameter 36.8
mm.
Objectives to be used lOX up to
lOOX.
Ideally suited
for
fluorescence work.
lOOX
objective used should have
built-in
adjustable iris diaphragm. Thickness of slide glass
to
be used, must be less than
1.2mm.
Low-Power
Condenser
Single lens
For low-power macro-objectives, e.g., 1.2X, 2X, & 3X
Plan Achromatic
These
condensers are not only capable of concentrating light-beam for better
illumination
of the image
field,
but also gives a great influence on the resolu-
tion
of microscope image, image contrast and depth of focus. In precise
observation and photomicrography, the use of an achromatic or aplanatic
condenser with the maximum numerical aperture 1.25 provided with an
oblique illumination device and a filter case is specially recommended.
—
9 —
ATTACHING
THE LENSES
Before attaching the objective and the eyepiece to the microscope, first
clean their outer lens surfaces.
Even
a slightly stained finger mark may
often
interfere with the image contrast.
1.
Mounting
the
Objectives
Take
special care in handling the objectives.
Before attaching the objectives on the nosepiece revolver, lower the
microscope stage sufficiently. Securing each objective with the fingers
of one hand, screw it
into
each nosepiece
hole with those of the
other hand (Fig. 4).
It
is recommended to
mount
the objectives
on the nosepiece or-
derly from low to high
powers so that the
magnification
of each
objective augments as
the
revolver is rotated
clockwise or counter-
clockwise.
Microscope Model L-Ke has on its upper surface of the nosepiece revolver
five
blank spots (Fig. 5) on each of which the objective magnification can
be Inked so
that,
by
looking
these Indica-
tions
from above, the
objective located below
can be identified
with-
out
having to turn
away
your
eyes
from
the
eyepiece.
When rotating the re-
volver, hold its outer
milled
rim with
your
thumb
and first finger,
but
do not push the
objective barrels, other-
wise alignment of the
objectives may be
trou-
bled.
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